Periods Of High Productivity Research Articles

Collaborative optimization of renewable energy power systems integrating electrolytic aluminum load regulation and thermal power deep peak shaving

Addressing renewable energy (RE) curtailment in power systems necessitates a comprehensive strategy leveraging peak regulation resources from both the power and load sides. On the power side, deep peak shaving of thermal power plants can mitigate surplus electricity during periods of high RE production. On the load side, energy-intensive industrial loads, characterized by large capacity and rapid adjustability, can respond effectively to energy deficits when RE is low. To enhance the peak regulation capacity for optimal RE accommodation, this paper proposes a collaborative optimization method combining electrolytic aluminum load (EAL) regulation with thermal power deep peak shaving (DPS). The study is initiated by developing a sophisticated peak regulation model for the electrolytic aluminum load (EAL), considering production characteristics, cost features, and safety constraints. Subsequently, a collaborative optimization model is formulated, integrating EAL regulation with thermal power deep peak shaving (DPS), aiming to minimize societal peak regulation costs (PRC). Applying this model to a practical regional grid in Yunnan Province reveals substantial reductions in RE curtailment rates, effective minimization of total social PRC, and enhanced operational economics of thermal power DPR under varying wind power scenarios. Notably, the proposed approach requires only minor adjustments to the EAL, ensuring production safety is maintained. This research provides valuable insights for the seamless integration of EAL into grid peak regulation services.

South Georgia marine productivity over the past 15 ka and implications for glacial evolution

Abstract. The subantarctic islands of South Georgia are located in the Southern Ocean, and they may be sensitive to future climate warming. However, due to a lack of well-dated subantarctic palaeoclimate archives, there is still uncertainty about South Georgia's response to past climate change. Here, we reconstruct primary productivity changes and infer Holocene glacial evolution by analysing two marine gravity cores: one near Cumberland Bay on the inner South Georgia shelf (GC673: ca. 9.5 to 0.3 cal. kyr BP) and one offshore of Royal Bay on the mid-shelf (GC666: ca. 15.2 cal. kyr BP to present). We identify three distinct benthic foraminiferal assemblages characterised by the dominance of Miliammina earlandi, Fursenkoina fusiformis, and Cassidulinoides parkerianus that are considered alongside foraminiferal stable isotopes and the organic carbon and biogenic silica accumulation rates of the host sediment. The M. earlandi assemblage is prevalent during intervals of dissolution in GC666 and reduced productivity in GC673. The F. fusiformis assemblage coincides with enhanced productivity in both cores. Our multiproxy analysis provides evidence that the latest Pleistocene to earliest Holocene (ca. 15.2 to 10.5 cal. kyr BP) was a period of high productivity associated with increased glacial meltwater discharge. The mid–late Holocene (ca. 8 to 1 cal. kyr BP), coinciding with a fall in sedimentation rates and lower productivity, was likely a period of reduced glacial extent but with several short-lived episodes of increased productivity from minor glacial readvances. The latest Holocene (from ca. 1 cal. kyr BP) saw an increase in productivity and glacial advance associated with cooling temperatures and increased precipitation which may have been influenced by changes in the southwesterly winds over South Georgia. We interpret the elevated relative abundance of F. fusiformis as a proxy for increased primary productivity which, at proximal site GC673, was forced by terrestrial runoff associated with the spring–summer melting of glaciers in Cumberland Bay. Our study refines the glacial history of South Georgia and provides a more complete record of mid–late Holocene glacial readvances with robust chronology. Our results suggest that South Georgia glaciers were sensitive to modest climate changes within the Holocene.

Origin and significance of macroscopic organic aggregates from the lacustrine Aptian Crato Konservat-Lagerstätte

The Crato Konservat-Lagerstätte is one of the main Mesozoic fossil sites from Gondwana, recording a wide diversity of terrestrial and non-marine aquatic fossils of great paleobiological and evolutionary significance. This conservation deposit is recorded in a 9 m-thick interval of laminite, microbialite, and grainstone deposited in a lake system with variable water level, alternating moments of hypersaline and freshwater conditions. Despite numerous studies describing new species of plants, arthropods, fish, pterosaurs, birds, and many others, there remains a significant gap in our understanding of the most common and archetypal fossils, which are the rod-shaped macrofossils found on bedding surfaces in distinct stratigraphic intervals of the Crato Konservat-Lagerstätte. The rod-shaped macrofossils are up to 1.6 cm-long and 0.1 cm-wide, straight to curved compressions that preserve pyritized microfossils. Here we interpret the rod-shaped macrofossils as macroscopic organic aggregates that sank into the lakebed in a process called lake snow. During high organic productivity periods in the epilimnion, planktonic organisms thrived and produced exopolymers responsible for aggregation. Their concentrations in the limestone bedding planes reflect intensity of lake snow and environmental seasonality. Aggregates are prolate particles that are commonly oriented, suggesting their transport as bedload for short distances, which was facilitated by biostabilization by microbes and their exopolymers. Finally, pyritization was mediated by microbial communities living in the lakebed.

Are the bibliometric growth patterns of excellent scholars similar? From the analysis of ACM Fellows

The growth of excellent scholars provides paradigmatic career paths leading to research success, as their research capabilities ultimately manifest as fluctuations in bibliometric indexes. Examining the commonalities in the trajectories of these bibliometric indexes displays the universal characteristics of their growth process, and furtherly shows exemplary routes to scientific success. In this study, we examine 287 excellent scholars elected as ACM Fellows in the field of computer science from 2016s to 2020s. Based on their changes in productivity, impact, and comprehensive abilities, we categorize them into three categories, four categories, and six categories, respectively. Most of these scholars experience continuous growth in productivity during the early development stages, maintaining a prolonged period of high productivity in the mid-later maturity stages. Their impact rises smoothly and consistently, while the growth of their comprehensive abilities is relatively gradual, remaining at above-average levels in the mid-later maturity stages. Furthermore, the level of recognition within the scientific research community varies for different categories of scholars, and there are also differences in the growth patterns between scholars from Asia and those from Western regions.

WITHDRAWN: Optimizing smart building energy systems for sustainable living: A realistic approach to enhance renewable energy consumfaption and reduce emissions in residential buildings

The presented a groundbreaking and economical approach to enhancing the sustainability of residential buildings by optimizing smart building energy systems. This approach, which is instrumental in advancing the shift towards a sustainable future, focuses on maximizing occupant comfort while markedly diminishing the energy footprint and emissions of the built environment. The study offers a comprehensive techno-economic and environmental analysis of the system performance conducted on residential apartments in Baghdad, Iraq. The results are promising, showing that the system successfully transfers 75.6 MWh of renewable electricity to the local grid and utilizes an additional 120.42 MWh for the internal needs of the building and operation of electrical components. A key component of the system is the biomass heater, which meets over 70.2% of the heating demand, proving particularly effective during periods of low solar power availability and high electricity costs. This highlights the importance of integrating diverse energy sources to reduce dependence on the grid. The results also reveals that the costs associated with energy consumption are substantially offset by the revenue generated from selling excess renewable energy during high-production periods. This results in average monthly energy costs being maintained below $151.2/MWh over several years. This cost-efficiency is achieved by eschewing batteries and optimizing the dimensions of the heat pump. Additionally, the system demonstrates a low emission index of 12.85 kgCO2/MWh, indicating a potential reduction in CO2 emissions by 75.6 TCO2/year compared to traditional energy mixes.

Integrated transcriptome and microbiome analyses of residual feed intake in ducks during high production period

Residual feed intake (RFI) is a crucial parameter for assessing the feeding efficiency of poultry. Minimizing RFI can enhance feed utilization and reduce costs. In this study, 315 healthy female ducks were individually housed in cages. Growth performance was monitored during the high laying period, from 290 to 325 days of age. The cecal transcriptome and microbiome of 12 ducks with high residual feed intake (RFI) and 12 with low residual feed intake (LRFI) were analyzed. Regarding growth performance, the LRFI group exhibited significantly lower RFI, feed conversion ratio (FCR), and feed intake (Fi) compared to the HRFI group (p < 0.01). However, there were no significant differences observed in body weight (BW), body weight gain (BWG), and egg mass (EML) between the groups (p > 0.05). Microbiome analysis demonstrated that RFI impacted gut microbial abundance, particularly affecting metabolism and disease-related microorganisms such as Romboutsia, Enterococcus, and Megamonas funiformis. Transcriptome analysis revealed that varying RFI changed the expression of genes related to glucose metabolism and lipid metabolism, including APOA1, G6PC1, PCK1, and PLIN1. The integrated analysis indicated that host genes were closely linked to the microbiota and primarily function in lipid metabolism, which may enhance feeding efficiency by influencing metabolism and maintaining gut homeostasis.

Acoustic measurements of photosynthetically formed gas bubble distributions in Posidonia oceanica seagrass meadows

The formation of gas bubbles on seagrass leaves commonly occurs during periods of high productivity in many aquatic ecosystems. Gas bubbles produced by seagrass meadows and subsequently released to the atmosphere can be a major component of primary production that is not quantified by measurements of dissolved oxygen. Acoustic propagation measurements have been explored as a possible tool for estimating photosynthetically relevant properties in situ. However, a lack of knowledge of bubble densities and size distributions has hindered acoustic attenuation as a quantitative measurement technique. Here we explore using measurements of acoustic backscattering from gas bubbles in and above Posidonia oceanica seagrass meadows as a more direct method for estimating bubble densities and size distributions. Acoustic backscattering data for this study was collected in September 2023 in Biodola Bay, Elba Island, Italy, using 1i–16 kHz linear frequency modulated pulses. Inversions of the broadband acoustic data yielded log-normal bubble size distributions with mean sizes between 0.4 and 0.5 mm in agreement with previously reported values. Estimated bubble densities yielded predicted attenuations in line with those found by propagation experiments. Results demonstrate the possible use of direct acoustic backscattering measurements as a supplement to dissolved oxygen measurements to better estimate rates of gas production which in turn can be used to better understand seagrass ecosystem properties, such as productivity and health.

Organic Matter Enrichment Mechanisms in the Lower Cambrian Shale: A Case Study from Xiangandi #1 Well

In order to investigate the effect of primary productivity, organic matter dilution, and preservation on the accumulation of organic matter, geochemical data, and proxies of primary productivity, clastic influx, and redox conditions were obtained for organic-rich shales in the Cambrian Niutitang Formation. The primary productivity (total organic carbon [TOC], Mo, P, Ba, and Babio) and redox (Ni/Co, V/Cr, U/Al, and Th/U) proxies suggest the organic-rich shales were deposited in anoxic-euxinic conditions during periods of high primary productivity. Pyrite in the Niutitang Formation comprises spherical framboids, which also indicate that anoxic bottom waters were present during organic matter deposition. High primary productivity enhanced the organic C flux into the thermocline layer and bottom waters, which lead to the development of anoxic bottom waters owing to O2 consumption by microorganisms and organic matter degradation. The anoxic bottom waters were beneficial for the preservation of organic matter. In addition, Ti/Al ratios correlate well with TOC contents throughout the Niutitang Formation, indicating that clastic input increased the burial rate and prevented organic matter degradation during deposition. Therefore, the accumulation of organic matter in the Niutitang Formation was controlled mainly by primary productivity rather than bottom-water redox conditions.

INFLUENCE OF PARATYPIC FACTORS ON THE FERTILITY OF DAIRY COWS AND REPLACEMENT HEIFERS

The results of researching the influence of the season, air temperature, age, stage of lactation, insemination number and daily milk yield on the fertilization of heifers and cows under different housing technologies are presented. It was established that the best fertilization was demonstrated by heifers kept in tethered housing at PE Agroprogres. Nevertheless, the fertilization rate of cows among the farms under study was the highest under free housing (p&lt;0.001). By months of the year, in general, on all farms, a trend of a greater number of inseminations of heifers was observed in spring and summer, although no clear dependence was established. The share of fertile inseminations of heifers of PE Agroprogress varied from 56% in October to 92% in June. Fertilization of heifers at SE EFs named after Dekabrists and Kutuzivka had less variability: from 47% in February to 70% in May in the first farm and from 46% in May to 60% in July in the second farm, respectively. At PE Agroprogres and SE EF named after Dekabrists, there was a tendency to increase the fertilization of heifers at the air temperature above 20 ºС. Cows of PE Agroprogres and SE EF named after Dekabrists had the lowest fertilization rate at temperatures below -10 ºC. There was also a trend of its increase with an increase in air temperature above 20 ºC. It was established that at PE Agroprogres (tethered housing) a clear trend of increasing the fertility of cows was observed during the period of summer open air housing, at SE RF named after Dekabrists this trend is almost imperceptible, and the opposite dependence has been established at SE EF Kutuzivka (year-round free housing keeping with feeding on walking platforms). At all studied farms, there was a clear tendency in decrease of the fertilization of cows during the period of high milk productivity. Cows of PE Agroprogres and SE EF Kutuzivka with a daily milk yield of more than 40 kg of milk were fertilized worse by 1-4% (р&lt;0.1) and 5-6% (р&lt;0.001) than animals with a lower milk yield. Cows of the SE EF named after Dekabrists with a daily milk yield of more than 30 kg also had 8-9% (p&lt;0.001) worse fertilization compared to animals with lower productivity. At all studied farms, the highest percentage of fertilization was characterized by heifers at their first insemination, and among cows were animals of the first and second calving. According to all inseminations, the average day of lactation of cows with their artificial insemination was 38-54 days longer at SE EF named after Dekabrists in comparison with PE Agroprogres and SE EF Kutuzivka (p&lt;0.001). The share of fertilized cows during the breeding period up to 90 days after calving was lower by 6% At PE Agroprogres, and by 9% at SE EF named after Dekabrists, and by 6% at SE EF Kutuzivka than in the mid-lactation period (91-180 days) (р&lt;0.001).

Rozwój innowacyjnych hubów energetycznych – panaceum na trudne czasy?

The Energy Hub concept can be defined as a central point where multiple energy carriers meet and the corresponding energy flows can be processed, conditioned, stored and ultimately distributed according to demand requirements in an optimal manner. The energy node modeling concept describes the relationship between input and output energy flows and can be used to optimize energy consumption during planning and operation. The hub can store surplus energy generated by photovoltaics for a long time and cover electricity and heat needs, even during periods of high demand or low renewable production. The research goal of the article is primarily to present the concept of innovation in the field of energy and to identify key energy hubs for the development of the modern economy, as also indicated by one of the authors of the innovation concept, Christensen, who treats distributed energy as the so-called a breakthrough innovation, i.e. one that will gradually replace the classic energy system from the market.

Fire frequency has a contrasting effect on vegetation and topsoil in subcoastal heathland, woodland and forest ecosystems, south‐east Queensland, Australia

AbstractEcosystems managed with contrasting fire regimes provide insight into the responses of vegetation and soil. Heathland, woodland and forest ecosystems along a gradient of resource availability were burnt over four decades in approximately 3‐ or 5‐year intervals or were unburnt for 45–47 years (heathland, woodland), or experienced infrequent wildfires (forest: 14 years since the last fire). We hypothesized that, relative to unburnt or infrequent fires, frequent burning would favour herbaceous species over woody species and resprouting over obligate seeder species, and reduce understorey vegetation height, and topsoil carbon and nitrogen content. Our hypothesis was partially supported in that herbaceous plant density was higher in frequently burnt vegetation; however, woody plant density was also higher in frequently burnt areas relative to unburnt/infrequently burnt areas, across all ecosystems. In heathland, omission of frequent fire resulted in the dominance of fern Gleichenia dicarpa and subsequent competitive exclusion of understorey species and lower species diversity. As hypothesized, frequent burning in woodland and forest increased the density of facultative resprouters and significantly reduced soil organic carbon levels relative to unburnt sites. Our findings confirm that regular burning conserves understorey diversity and maintains an understorey of lower statured herbaceous plants, although demonstrates the potential trade‐off of frequent burning with lower topsoil carbon levels in the woodland and forest. Some ecosystem specific responses to varied fire frequencies were observed, reflecting differences in species composition and fire response traits between ecosystems. Overall, unburnt vegetation resulted in the dominance of some species over others and the different vegetation types were able to withstand relatively high‐frequency fire without the loss of biodiversity, mainly due to high environmental productivity and short juvenile periods.

Chemicals-CO2 mechanisms of inhibiting steam heat transfer and enhancing oil film strip: Steam flow through the wall-adhering oil film surface in porous medium

The CO2 and Sodium Dodecyl Sulfate (SDS) assisted steam flooding technology was an effective approach addressed the persistent issues that have hindered the stable development of high-viscosity cold oil through steam injection. However, in the process of steam flow through porous media, the synergistic influence of the oil film adsorbed in near wellbore porous media, and the CO2-SDS on steam heat transfer has not been investigated. Steam heat transfer is the key factors affecting heavy oil recovery. The primary objective of this study was to research the effect of CO2-SDS on steam heat transfer and oil film stripping by designing experiments. The study results demonstrated that in the initial stage of displacement, the heat transfer resistance between the steam and the porous medium was increased by the oil film adsorbed in near wellbore area. In additional, the condensation mode of the steam was altered from bead condensing to film condensing by the composite thermal fluid flooding, preventing the steam heat dissipation near wellbore area and transferring more thermal to the long-distance area. At the later stage of displacement, the interfacial tension between oil-water and oil-gas was reduced by CO2-SDS, improving the fluidity of oil and providing the seepage channel for steam, and increasing the steam thermal sweep range. Compared to the sandpack experiment of steam flooding, the temperature at the output end of the sandpack model increased from 69.8 °C to 88.7 °C, indicating an expansion of the steam heat sweep range and successful long-distance heat transfer during composite thermal fluid flooding. In the process of composite thermal fluid flooding, the maximum displacement pressure difference increased from 2.28 MPa to 3.07 MPa, and the maximum oil recovery rate increased from 2.48 g/mL to 2.81 g/mL. The peak of the high production period was raised, resulting in a 40.97% to 51.86% increase in recovery rates.

A comparison of spatial and temporal drivers of stream metabolism

Abstract Stream metabolism provides insight into the functional processes that regulate trophic status, biomass, and nutrient cycling in streams. Comparative (spatial) analyses of streams generally do not account for shifting at‐site controls on stream metabolism over time and, thus, may not identify the primary controls on cross‐site differences in trophic status, biomass, and nutrient cycling over longer time scales. The spatial component included assessing environmental factors controlling stream metabolism (daily values) during a summer low‐flow period (August) at 17 wadable stream sites in four regions of the United States. Explanatory variables for the spatial analysis included discrete nutrients and physical parameters. The temporal component included assessing 12 of the 17 sites with more than 90 days of stream metabolism values, and continuous nitrate, photosynthetically active radiation (PAR), turbidity, maximum water temperature (°C) and stream stage (water surface elevation). Spatial analysis at the 17 sites during August (31 days) found that average gross primary production (GPP) ranged from 0.1 to 4 g O2 m−2 day−1 and ecosystem respiration (ER) from 0.37 to 6.4 g O2 m−2 day−1. Sites were primarily heterotrophic; however, some sites varied from autotrophic to heterotrophic daily. Multiple regression indicated that GPP was a function of orthophosphate, percent canopy cover, and the number of days since a high flow (R2 = 0.51), whereas ER was primarily a function of GPP (R2 = 0.40). Temporal patterns in daily stream metabolism were evaluated using at‐site autoregressive models at 12 streams with relatively complete, continuous records. PAR, nitrate and maximum water temperature were the dominant variables influencing GPP, and water depth and nitrate were the most common explanatory variables for ER models. The autoregressive components (i.e., GPP or ER for the previous day) had a strong influence on both GPP and ER except after spates, indicating that biomass may be the dominant control on metabolism rather than variability in environmental factors during stable‐flow periods. We found two dominant temporal metabolism regimes: a seasonal pattern with elevated spring metabolism followed by low stable summer metabolism and a temporally disturbed pattern which tended to occur in streams with frequent spates. These patterns were not indicated by differences in metabolism among streams during stable low‐flow conditions. Because streams are generally heterotrophic with only limited periods when production may be high, comparative analyses must estimate stream metabolism over a time scale representing at‐site spatial variability and account for controls on periods of high production to adequately characterise differences between streams.

Depositional conditions of siliceous microfossil-rich shale during the Ordovician–Silurian transition of south China: Implication for organic matter enrichment

Knowledge of the paleoenvironment is crucial to understand organic matter enrichment and shale gas development. Like organic matter, siliceous microfossils such as radiolarians and sponge spicules are widely distributed in Late Ordovician to early Silurian shales. However, there are few characterizations of the depositional conditions of siliceous microfossil-enriched layers. Here siliceous microfossil-rich shales from the Ordovician–Silurian transition in South China were selected for this study. We used major/trace element geochemistry to determine the sedimentary environment of siliceous microfossil-rich shale and to strengthen the understanding of the effect of siliceous microorganisms on organic matter enrichment. Our results show that most siliceous microfossils were deposited in anoxic reducing conditions with the presence of free hydrogen sulfide and accompanied by a moderately to weakly restricted seawater circulation. In addition, the nutrient-rich water bodies could upwell from the deep sea into the Yangtze Sea, and siliceous microfossil-rich shale was deposited during a period of high primary productivity. The shale layers of siliceous microfossils generally correspond to high gas-producing intervals and high organic matter abundance. The accumulation and preservation of organic matter in siliceous microfossil-rich shales is attributed to anoxic benthic conditions, high levels of primary productivity and flourishing of siliceous microorganisms. This study addresses the knowledge gap of the depositional conditions in siliceous microfossil-rich shale, and can help better understand the history of organic matter accumulation.

Calcification response of planktic foraminifera to environmental change in the western Mediterranean Sea during the industrial era

Abstract. The Mediterranean Sea sustains a rich and fragile ecosystem currently threatened by multiple anthropogenic impacts that include, among others, warming, pollution, and changes in seawater carbonate speciation associated to increasing uptake of atmospheric CO2. This environmental change represents a major risk for marine calcifiers such as planktonic foraminifera, key components of pelagic Mediterranean ecosystems and major exporters of calcium carbonate to the sea floor, thereby playing a major role in the marine carbon cycle. In this study, we investigate the response of planktic foraminifera calcification in the northwestern Mediterranean Sea on different timescales across the industrial era. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta, and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples. The results of our study suggest substantial different seasonal calcification patterns across species: G. bulloides shows a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters indicate that controls on seasonal calcification are species-specific. Interannual analysis suggests that both G. bulloides and N. incompta did not significantly reduce their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight. The comparison of these patterns with environmental data reveals that optimum growth conditions affect positively and negatively G. bulloides and G. truncatulinoides calcification, respectively. Sea surface temperatures (SSTs) have a positive influence on N. incompta and G. truncatulinoides calcification, while carbonate system parameters appear to affect positively the calcification of three species in the Gulf of Lions throughout the 12-year time series. Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the pre-industrial era. Several lines of evidence indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a weight reduction between pre-industrial and post-industrial Holocene and recent data, with G. truncatulinoides experiencing the largest weight loss (32 %–40 %) followed by G. bulloides (18 %–24 %) and N. incompta (9 %–18 %). Overall, our results provide evidence of a decrease in planktic foraminifera calcification in the western Mediterranean, most likely associated with ongoing ocean acidification and regional SST trends, a feature consistent with previous observations in other settings of the world's oceans.

Petrography and geochemistry of the iron-rich rocks in the banded iron formation of the Chilpi Group, Central India: Implications on the level of oxygen in the Paleoproterozoic atmosphere before the “Proterozoic iron ore gap”

The Chilpi Group (2050–1850 Ma) in the Bastar Craton contains Banded Iron Formation (BIF) deposited immediately after the Great Oxidation Event but before the “Proterozoic iron ore gap”. Baseline geochemical data generated from this crucial period of Earth's history representing the transition from an initial high productivity period followed by productivity collapse, thereby delaying the evolution of biota, are interpreted in terms of the redox state of the ocean and atmospheric oxygen content. Presence of chamosite, greenalite and siderite in the ironstones of the Chilpi Group, identified during present analysis, provide valuable information regarding the redox state of the shallow sea. Geochemical analyses reveal high concentrations of Fe2O3total and SiO2 (average ~ 87.85 wt%) in iron-rich bands. Trace elements commonly enriched in detrital phases (e.g. Sc, Hf, Nb, Th and Zr) show good correlation with total REE concentration, but these have concentration below the cut-off limit defined for detrital sediments (except 3 samples). Higher concentration of these elements in greenalite/chamosite-rich samples indicates accumulation of these elements in greenalite/chamosite during primary precipitation. Most of the samples have low concentrations of Al2O3 (<5 wt%) and TiO2 (<0.5 wt%), but some chamosite-bearing samples show enrichments of Al2O3 (up to ~20 wt%). Post-Archean Australian Shale normalised rare earth elements with Y (REEY) patterns, showing a superchondritic Y/Ho ratio (average 32.15) and positive La, Gd and Y anomalies, indicate the preservation of seawater like signatures. Though a low positive Eu-anomaly, and Al/(Al + Fe + Mn) versus Fe/Ti plot suggest seawater signature with possible mixing of hydrothermal fluids and/or <10 % detrital components, preservation of seawater signatures and no involvement of high-temperature hydrothermal fluids are deduced from Eu/Sm versus Sm/Yb and Eu/Sm versus Y/Ho patterns. The Eu/Sm and Y/Ho ratios lower than the seawater and a mixing trend away from oceanic hydrothermal solution indicate possible mixing of freshwater with seawater for the observed REEY patterns. Redox-sensitive trace element ratios indicate a dysoxic to suboxic-anoxic condition in the depositional basin. Presence of oolitic textures and occurrence of chamosite support the shallow water (<60 m water depth) and anoxic condition in the depositional basin. The oxygen content of 10−3–10−5 times the present atmospheric level in the atmosphere is inferred for the period during the deposition of the BIF.

Influences of Seasonal Variability and Potential Diets on Stable Isotopes and Fatty Acid Compositions in Dominant Zooplankton in the East Sea, Korea

Despite their crucial roles in transporting primary productions in marine food webs, the trophic dynamics of zooplankton throughout the seasons have rarely been studied. In this study, four dominant zooplankton taxa with phytoplankton size composition and productivity were collected over four seasons in the East Sea, which is known to change more rapidly than global trends. We then analyzed the δ13C and δ15N values and fatty acid composition of zooplankton. The heavy δ13C values in February and August 2021 were observed with high concentrations of total chlorophyll-a, and the δ13C differences among the four zooplankton taxa in the coastal region (site 105-05) were most pronounced in February 2021. The relative amounts of eicosapentaenoic acid (C20:5(n-3)) and docosahexaenoic acid (C22:6(n-3)), indicators of phytoplankton nutritional quality, were also highest in February 2021. Non-metric multivariate analyses showed dissimilarity among zooplankton taxa during the high productivity period based on chlorophyll-a concentrations (51.6%), which may be due to an increase in available foods during the highly productive season. In conclusion, the dietary intake of zooplankton can be reduced by the transition of phytoplankton, which has important implications for the impact of climate change on planktonic ecosystems in the East Sea.

Seasonal and tidal controls of the quantity and quality of dissolved organic matter at the marsh creek-estuarine interface

Tidal marshes are an important source of dissolved organic matter (DOM) to estuaries, and DOM plays an integral role in regulating water quality and health of coastal ecosystems. However, our understanding of temporal patterns of DOM quantity and composition at the marsh-estuarine interface is limited. This study investigated temporal changes in colored DOM (CDOM), an important component of dissolved organic carbon (DOC), exchanged across a brackish marsh-estuarine system. The sources of DOC were examined using stable carbon isotope values whereas the sources of CDOM were based on spectroscopic properties, including absorbance and fluorescence excitation-emission matrices (EEMs). Samplings at the Taskinas marsh creek-interface in Virginia (USA) captured a range of tidal stages, seasons, and environmental conditions over a three-year timeseries. Water from low and high tides was used to represent marsh and estuarine endmembers, respectively. Absorbance of CDOM at 440 nm ranged from 0.83 to 6.75 m-1, and the highest values were found during low tides (mean 2.78 ± 0.21 m −1). EEMs were composed of three humic-like components (C1, C2, C3) and one protein-like component (C4). Generally, the terrestrial humic-like (C1) and marine humic-like (C2) components were more abundant than other measured components. Seasonally, CDOM absorbance was highest in spring and summer. Contributions of CDOM from terrestrial sources increased in spring during periods of high runoff and peaked in summer during periods of high marsh productivity. Higher contributions of terrestrially derived CDOM were also measured in fall during periods of plant senescence. The aquatic component (C4) was higher during periods of increased phytoplankton production and during periods of high microbial respiration of terrestrial and planktonic organic matter. Although the amount of marsh exported CDOM varied with season, its composition varied considerably less, especially with respect to autochthonous CDOM. In a focused study in 2018, inferences about the terrestrial versus estuarine sources of CDOM were compared to source inferences made using measurements of stable carbon isotopes (δ13C) of DOC and DIC. δ13CDOC values ranged from −32.25 to −25.91‰, indicative of wetland organic matter and humic-like DOM; δ13CDIC ranged from −9.69 to −3.12‰, consistent with groundwater and estuarine sources. Overall, CDOM and stable isotope measurements indicate that humic materials were the primary source of DOM at this marsh-estuarine interface, including inputs from marsh plants and soils and products from microbial degradation of marsh and terrestrial materials, with lesser contributions from aquatic sources.

Palaeoceanographic and palaeoenvironmental controls on late Quaternary benthic foraminifera of the western continental slope of South Africa

Benthic foraminifera from two gravity cores recovered on the western continental slope (3522 and 3631 m water depth) of South Africa were studied to determine bottom water conditions and benthic environments over late Quaternary glacial-interglacial cycles. Benthic foraminifera assemblages and the carbon isotopic composition (δ13C) of Cibicidoides wuellerstorfi and Globoconella inflata were used to reconstruct palaeoenvironmental conditions. The assemblages reflect influences from substrate, productivity (seasonal and annual variations in the flux of organic matter, such as phytodetritus to the seafloor) and bottom water oxygenation. Uvigerinid forms were found to be distributed along bathymetric depths that also reflect oxygenation of bottom waters, where hispid and hispidocostate forms were more abundant at depths of oxygen-enriched bottom waters on the lower slope. These uvigerinids and other benthic species such as Epistominella exigua were also found to benefit from periods of high productivity. Palaeoproductivity increased during glacial periods but decreased sharply by a difference of ∼1‰ in δ13C during glacial terminations, reflecting a less nutrient-rich bottom water signal. During interglacial periods, epifaunal foraminifera and taxa adapted to oxygen-enriched environments, such as Cibicidoides spp. and high oxygen assemblages increased in abundance and were correlated to the less radiogenic regional εNd signals, while the abundance of high-productivity fauna and assemblages, associated with the nutrient-rich Southern Component Water, and that are adapted to a high organic matter flux and low oxygen conditions, decreased. Interglacial periods were reflected to exhibit benthic environments that are more oligotrophic, while glacial periods were interpreted to reflect more eutrophic conditions.

Experimental study on thermochemical composite system huff-n-puff process in ultra-heavy oil production

The thermochemical composite system huff-n-puff has been widely employed for oil reservoirs characterized by thinner layers and higher oil viscosity, which however suffers less information on residual oil distribution, the diffusion behaviors of injected fluids, and property variation of oil, etc. In this paper, a 3D physical model is employed to investigate the diffusion behaviors of the injected fluid (viscosity reducer, CO2, and steam) in porous media and their synergistic effect on ultra-heavy oil recovery. The influences of thermochemical composite system on oil properties are carried out to investigate their mechanisms on oil viscosity reduction. Based on the 3D physical model, huff-n-puff experiments are carried out to study the thermochemical composite system’s advantage of enhanced heavy oil recovery. The properties of the produced oil from a production well in Shengli Oilfield are collected and analyzed to test the feasibility of thermochemical composite flooding. The results show that there is a synergistic effect on oil viscosity reduction when the viscosity reducer is combined with CO2 and steam (the oil viscosity decreases by 84.38 %). During viscosity reducer injection, most of the viscosity reducer is distributed around near-well zone of the front-well section. The uneven distribution of viscosity reducer in the 3D model is alleviated by CO2 injection, which brings the viscosity reducer to the far-well zone. For the steam, it can improve the mobility of crude oil and reduce the differences in the asphaltene content between layers. Therefore, even after five cycles of huff-n-puff, relatively high oil recovery can still be obtained (oil recovery rate above 3.35 %). In the oil field application, the oil viscosity increases gradually in one huff-n-puff cycle, while the disassociation effect of viscosity reducer becomes weaker as the huff-n-puff cycles increase. Due to the synergistic effect of thermochemical composite system, it can maintain a period of high oil production for the single well (>1700 tons/cycle) in Shengli Oilfield.